1. Field of the Invention
This invention relates to a chair, in particular a work or office chair, with a backrest rod adjustable in inclination with respect to the seat and a backrest slideable thereon, which can be displaced with an adjustment device when the backrest rod is tilted backward in the direction of the seat.
2. Description of Prior Art
The known chairs of this type offer excellent seating comfort because, on the one hand, they provide a definite support of the back of the user in the initial or working position as a result of the practically vertical position of the backrest and, on the other hand, permit relaxed sitting when the backrest rod is tilted back. When the backrest rod is tilted back, the upper torso of the user does not simply perform a pivot motion, but there is motion in which several movement components are superimposed on each other. Because the backrest performs an additional downward movement when the backrest rod is tilted back, relative movement between the back of the user and the backrest is avoided or at least reduced to a point which is no longer noticeable.
As shown in European patent applications 0,085,670 A1 and 0,176,816 A1 and German patent application 2,916,897 A1, compensation of the relative movement between the body of the user and the backrest can be attained in different types of chairs in constructively different ways. The chair may be a synchronized chair, in which a downward tilt of the seat carrier supporting the seat causes a forced backward tilt of the backrest rod with a larger tilt angle. It is also possible to make the seat carrier so that it can be slid out from the bracket. As taught by these known chairs, an expensive and complicated adjustment device, which does not always operate trouble-free and operationally safe, is always required for compensation of the relative movement between the body of the user and the backrest, which occurs when the tilt of the backrest rod is changed.
Either multi-link lever chains are used, as shown in European patent application 0,176,816 A1 or pairs of transmission levers and carrier elements are used, as shown in European patent application 0,085,870 A1. In this case many parts are required for the adjustment device. The same is true for a chair taught by German patent application 2,916,897 A1, in which the backrest is displaced on the backrest rod in the direction towards the seat when the seat is pulled out.